Numerous diseases and pathophysiological states are associated with deviations from normal concentrations of analytes in a patient's blood or tissues. Congestive heart failure (CHF), for instance, causes significant morbidity and mortality, and the healthcare expenditure for this disease is substantial. While in vitro diagnostic assays to measure various analyte levels in the blood are now in use, these assessments are point-in-care assessments that do not provide the clinician a complete profile of a patient's changing status. The inability to determine when a patient's CHF is worsening (before a patient gains several pounds in weight and/or edema is greatly increased) until the patient has a doctor's appointment or requires hospitalization will result in a delay of treatment. Moreover, required changes to the patient's therapy will be delayed.
Implantable biosensors have recently become an important tool for analyzing and quantifying analyte compositions in a patient's blood which could be used for initiating therapy, conducting diagnostics or monitoring. Cells and/or tissues within the patient's body may act as sensors to detect and monitor these analyte concentrations. For early detection of disease or change in disease such as CHF, it is desirable for the implantable biosensor to be sensitive to changes in analyte levels.